1. Field of the Invention
The present invention relates to an ink jet recording apparatus capable of a high-quality recording, and more particularly to a recording apparatus having an exchangeable ink jet head and a recovery control method (maintenance method) therefor.
2. Related Background Art
An ink jet recording apparatus is widely employed in a printer, a copying apparatus and the like for reasons of e.g. a low noise, a low running cost and an easy compact formation of the apparatus. In such ink jet recording apparatus, foreign substances such as unnecessary ink droplets and paper dusts may be deposited in the vicinity of discharge ports by fine ink droplets generated in addition to a main ink droplet when ink is discharged or by rebound of the ink droplet landing on a recording medium. Such deposition of the foreign substances may result in a deviation of an ink discharging direction or a landing position, an ink discharge failure or a deterioration of the image quality.
As the ink jet recording apparatus is a system for converting input image data into an output image by way of a liquid constituting the ink, a maintenance technology for achieving satisfactory ink droplet discharge is a very important factor. In the following, there will be briefly described principal phenomena requiring the maintenance (recovery operation).                (a) In the course of recording of input image data, among plural discharge ports provided in an ink jet head, ink evaporates in a non-discharging discharge port, whereby the ink in the discharge port becomes viscous and cannot be discharged stably with an ordinary discharge energy, thereby resulting in a discharge failure;        (b) In the recording, the ink droplet discharged from a nozzle includes a main ink droplet and fine droplets (called mist), which are deposited around the ink discharge port of the ink jet head, thereby hindering straightness of the ink discharge; and        (c) In case a bubble is present in an ink reservoir in the ink jet head, a gas penetrating through a material constituting the ink jet head is taken into such bubble to cause a growth of the bubble, which is inflated at a temperature elevation in the printing operation, thereby hindering an ink supply from an ink tank and eventually resulting in a defective printing.        
For solving such phenomena, following maintenance technologies are known.                (a) According to a time or an environment in which the ink discharge is not executed, a discharge of a predetermined amount is executed separately from the printing operation for forming an image on a recording medium, thereby discharging the viscosified ink (hereinafter this operation being called a preliminary discharge).        (b) A number of discharges of the ink droplet from the discharge port is counted, and, when the count exceeds a predetermined number, a surface of the ink jet head on which the discharge ports are formed (hereinafter such surface being called a face) is wiped with a rubber blade or the like to remove the deposited ink (hereinafter such operation being called a wiping).        (c) A recovery operation is executed by sucking the ink from the discharge port by a pump, thereby discharging the ink in the discharge port (hereinafter such operation being called suction recovery).        
Also in an ink jet recording apparatus in which the ink jet head and the ink tank are mutually separable and the ink tank is exchangeable, the suction recovery is executed also after the exchanging of the ink tank.
Now, the wiping operation and the suction recovery operation will be explained briefly with reference to the accompanying drawings.
FIG. 1 explains the wiping operation. There are shown a rubber blade 1101 for wiping, a face 1102 to be wiped, an ink discharge port 1103, a deposited ink 1104 to hinder the discharge, and a wiping direction 1105. In the wiping, the rubber blade 1101 pressed to the ink jet head as illustrated is moved in a direction 1105 thereby bringing the deposited ink 1104 in contact with the blade and wiping it off from the face.
FIG. 2 is a view explaining the suction recovery. There are shown an ink jet head 1201, an ink discharge nozzle 1202, a face 1203, a suction cap 1204, an ink discharge tube 1205, and a suction pump 1206 for generating a negative pressure for sucking the ink. The suction recovery operation is executed by contacting or sealingly pressing a generally rubber suction cap 1204 to the face 1203 and rotating the suction pump 1206 in a direction indicated by an arrow 1207 to generate a negative pressure thereby sucking the ink in the ink jet head 1201 from the ink discharge port 1202 into the suction cap 1204 and discharging it through the ink discharge tube 5.
In the recent ink jet recording apparatus for which a higher image quality and a higher speed are required, kinds of loaded inks and number of the ink discharging ports are drastically increased in comparison with those in several years ago, and such maintenance technologies are becoming a large issue.
Also for a lower cost and a higher recording quality of the recording apparatus, there is proposed an ink jet head cartridge in which an ink jet head portion and an ink tank portion are constructed integrally and which is rendered exchangeable on the recording apparatus. In the ink jet head of such type, in case the user makes a selection among the plural ink jet head cartridges different in the types or colors of the inks for mounting on the recording apparatus, there is conceived a case where the main body of the recording apparatus and cartridge (type of ink in the ink jet head cartridge) cannot be matched and a maintenance suitable for the ink jet head cartridge (type of ink in the ink jet head cartridge) cannot be executed. It is therefore proposed to provide the ink jet head cartridge with a semiconductor memory storing characteristics of the ink jet head cartridge such as the type of the ink and the number of the discharge ports.
Also in the aforementioned exchangeable ink jet head, being integral with the ink tank, may show a deterioration in the characteristics of the ink jet head by a shock in transportation or an environmental change. Therefore, at an exchange to a new ink jet head, the recording apparatus has to execute a recovery operation for filling the ink jet head with the ink thereby refreshing the ink jet head.
Thus, in order to improve the operability at the exchange of the ink jet head and to achieve an optimum recording after the exchange of the ink jet head, Japanese Patent No. 3176343 (patent reference 1) describes a technology of executing a recovery operation of a larger amount for an ink jet head that has been judged as exchanged, than that for an ink jet that has been judged as not exchanged.
A method for detecting the ink jet head exchange described in the patent reference 1 reads a serial number attached to the ink jet head and judges that the ink jet head has not been exchanged in case the read serial number is same as a serial number read previously, and that ink jet head has been exchanged in case the read serial number is different from a serial number read previously (cf. FIG. 3). Also the recovery operation is so controlled that a recovery amount becomes larger in a case where the ink jet head is exchanged than in a case where the ink jet head is not exchanged (cf. FIG. 4).
On the other hand, in a recording apparatus of a configuration in which the ink tank and the ink jet head are separable and the ink tank has to be detached from the recording apparatus in case of detaching the ink jet head from the recording apparatus, since the ink tank also is detached at the detaching of the ink jet head, whereby a joint portion between the ink tank and the ink jet head is exposed to the air to cause an evaporation of the ink from such joint portion, and there is concerned a defective ink supply at the joint portion between the ink tank and the ink jet head in a mounted state. Also in case the detached ink jet head is handled improperly or roughly, there may be caused an ink leakage from the joint portion or from the nozzles, thereby leading to a defective ink supply in the joint portion or in the ink jet head.
Thus, in case the ink jet head is detached and mounted without the exchange of the ink jet head, a suction recovery is necessary in order not to cause a defective ink supply. However, in case the ink jet head is not exchanged but merely detached and re-placed, a recovery operation of a level at the exchange of the ink jet head is not required since the ink has been supplied in the head prior to the detachment of the ink jet head.
However, the technology described in the patent reference can detect the exchange of the ink jet head but cannot detect the detaching and mounting thereof, so that, in case the ink jet head is judged as not exchanged, the recovery operation is not executed until an uncapped period or a time elapsing from the previous suction operation exceeds a threshold value, whereby a defective ink supply may occur in case the ink jet head is detached and mounted.
In case a recovery operation is always executed even in case the ink jet head is judged as not exchanged in order to the reduce the defective ink supply caused by the detaching and mounting of the ink jet head, the recovery operation is conducted even in case the detachment and mounting of the ink jet head is not executed and thus the recovery operation is not necessary, so that the ink amount consumed in the recovery operation is elevated thereby leading to drawbacks of an elevated running cost, and a large used ink absorbent member is required for absorbing the used ink, thereby leading to an increased dimension of the recording apparatus.